A number of types of domestic fan are known. It is common for a conventional fan to include a single set of blades or vanes mounted for rotation about an axis, and driving apparatus mounted about the axis for rotating the set of blades. Domestic fans are available in a variety of sizes and diameters, for example, a ceiling fan can be at least 1 m in diameter and is usually mounted in a suspended manner from the ceiling and positioned to provide a downward flow of air and cooling throughout a room.
Desk fans, on the other hand, are often around 30 cm in diameter and are usually free standing and portable. In standard desk fan arrangements the single set of blades is positioned close to the user and the rotation of the fan blades provides a forward flow of air current in a room or into a part of a room, and towards the user. Other types of fan can be attached to the floor or mounted on a wall. The movement and circulation of the air creates a so called ‘wind chill’ or breeze and, as a result, the user experiences a cooling effect as heat is dissipated through convection and evaporation. Fans such as that disclosed in U.S. D Pat. No. 103,476 and U.S. Pat. No. 1,767,060 are suitable for standing on a desk or a table. U.S. Pat. No. 1,767,060 describes a desk fan with an oscillating function that aims to provide an air circulation equivalent to two or more prior art fans.
A disadvantage of this type of arrangement is that the forward flow of air current produced by the rotating blades of the fan is not felt uniformly by the user. This is due to variations across the blade surface or across the outward facing surface of the fan. Uneven or ‘choppy’ air flow can be felt as a series of pulses or blasts of air and can be noisy. Variations across the blade surface, or across other fan surfaces, can vary from product to product and may even vary from one individual fan machine to another.
In a domestic environment it is desirable for appliances to be as small and compact as possible due to space restrictions. It is undesirable for parts to project from the appliance, or for the user to be able to touch any moving parts of the fan, such as the blades. Some arrangements have safety features such as a cage or shroud around the blades to protect a user from injuring himself on the moving parts of the fan. U.S. D Pat. No. 103,476 shows a type of cage around the blades however, caged blade parts can be difficult to clean.
Other types of fan or circulator are described in U.S. Pat. No. 2,488,467, U.S. Pat. No. 2,433,795 and JP 56-167897. The fan of U.S. Pat. No. 2,433,795 has spiral slots in a rotating shroud instead of fan blades. The circulator fan disclosed in U.S. Pat. No. 2,488,467 emits air flow from a series of nozzles and has a large base including a motor and a blower or fan for creating the air flow.
Locating fans such as those described above close to a user is not always possible as the bulky shape and structure mean that the fan occupies a significant amount of the user's work space area. In the particular case of a fan placed on, or close to, a desk the fan body or base reduces the area available for paperwork, a computer or other office equipment. Often multiple appliances must be located in the same area, close to a power supply point, and in close proximity to other appliances for ease of connection and in order to reduce the operating costs.
The shape and structure of a fan at a desk not only reduces the working area available to a user but can block natural light (or light from artificial sources) from reaching the desk area. A well lit desk area is desirable for close work and for reading. In addition, a well lit area can reduce eye strain and the related health problems that may result from prolonged periods working in reduced light levels.